Princeton's WordNet

1. vitamin D, calciferol, viosterol, ergocalciferol, cholecalciferol, D(noun)

   a fat-soluble vitamin that prevents rickets

   Synonyms:
   ergocalciferol, cholecalciferol, calciferol, five hundred, vitamin D, viosterol

   Antonyms:
   ordinal

2. five hundred, 500, D(noun)

   the cardinal number that is the product of one hundred and five

   Synonyms:
   ergocalciferol, cholecalciferol, calciferol, five hundred, vitamin D, euchre, viosterol

   Antonyms:
   ordinal

3. D, d(adj)

   the 4th letter of the Roman alphabet

   Synonyms:
   ergocalciferol, cholecalciferol, calciferol, five hundred, vitamin D, viosterol

   Antonyms:
   ordinal

4. five hundred, 500, d(adj)

   denoting a quantity consisting of 500 items or units

   Synonyms:
   d, five hundred

   Antonyms:
   ordinal